Exodus 7:8

6Moses and Aaron did so. As the LORD commanded them, so they did.

7Moses was eighty years old, and Aaron eighty-three years old, when they spoke to Pharaoh.

8The LORD spoke to Moses and to Aaron, saying,

9“When Pharaoh speaks to you, saying, ‘Perform a miracle!’ then you shall tell Aaron, ‘Take your rod, and cast it down before Pharaoh, and it will become a serpent.’”

10Moses and Aaron went in to Pharaoh, and they did so, as the LORD had commanded. Aaron cast down his rod before Pharaoh and before his servants, and it became a serpent.